Western blot analysis (WB) is a semi-quantitative biochemistry assay used to assess the concentration of a protein and its modifications in a sample. In this assay, sample cells are first lysed to obtain their protein for analysis. Next, the sample proteins are denatured and run on an SDS-PAGE gel to separate them by molecular weight, prior to their transfer to a membrane (typically made of nitrocellulose or PVDF). Antibodies are then used to stain the membrane for the protein, for detection by film or a specialized camera.
Immunoprecipitation (IP) is a technique where an antibody is used to precipitate a particular protein from a sample lysate, thereby isolating the protein for concentration, binding partner identification, etc. To isolate the protein, antibodies are generally coupled to magnetic beads or sepharose before the sample lysate is added.
RNP immunoprecipitation (RIP) is a variant of chromatin immunoprecipitation (ChIP) where ribonucleoproteins and their associated RNA are targeted by antibodies rather than DNA-binding proteins and DNA. Additionally, due to the use of RNA, an RT-PCR or cDNA sequencing step is needed for analysis.
Immunoelectron microscopy is a technique for examining proteins in higher resolution than light microscopes using an electron microscope and antibodies conjugated to gold particles.
Immunohistochemistry (IHC) is a technique used to visualize a particular protein in its original tissue context. In this technique, frozen or paraffin-embedded tissue is stained with antibodies and usually counterstained with hematoxylin and eosin.
Immunocytochemistry (ICC) is a technique used to visualize a particular protein in cells outside of their original tissue context. In this technique, cells are stained with fluorescent antibodies and are usually counterstained with DAPI (or generally a DNA stain) to visualize nuclei. At Proteintech, we use ICC and immunofluorescence (IF) interchangeably to describe this technique.
Flow cytometry (FC) is a technique used to identify a subset of cells expressing a particular protein and then quantify its expression levels. It is commonly used for membrane proteins but can also be used to examine intracellular proteins if the cells to be examined are permeabilized prior to antibody staining. In this technique, cells are stained with fluorescent antibodies and usually counterstained with viability dyes in order to examine living cells only.Fluorescence-activated cell sorting (FACS) is a type of flow cytometry in which cell populations are sorted based on their fluorescence levels.
Co-immunoprecipitation (CoIP) is a technique where an antibody against one component of the protein complex is used to precipitate the entire complex in order to study its protein binding partners and identify novel associated proteins.
Chromatin immunoprecipitation (ChIP) is a technique used to identify the DNA binding sites of a particular protein. In this technique, proteins are cross-linked to DNA in living cells, followed by cell lysis and DNA shearing. The analyzed protein is then precipitated from the solution using an antibody, typically coupled to magnetic beads or sepharose, and the DNA is analyzed by sequencing.
Direct enzyme-linked immunosorbent assay (ELISA) is a technique used to quantify proteins in a sample. The protein sample is first immobilized on a surface (e.g., a plastic plate) and incubated with an antibody conjugated with an enzyme. The enzyme attached to the antibody converts the substrate, producing a color, fluorescent, or electrochemical signal that can then be quantified.
Indirect enzyme-linked immunosorbent assay (ELISA) is a version of ELISA, where an unconjugated antibody specific to a particular protein is used to bind to an immobilized protein, with a secondary enzyme-conjugated antibody against the primary antibody used for the detection. This setup allows amplification of the signal.
Sandwich enzyme-linked immunosorbent assay (ELISA) is a version of ELISA, where an immobilized antibody on a surface (capture antibody) is used to capture a particular protein from a sample. After washing, a second antibody conjugated with an enzyme (detection antibody) is used to detect and measure levels of the captured protein.